Calibration module for a tester and tester

ABSTRACT

A calibration module for a tester, for testing a device under test, includes a pair of RF-channel terminals, a calibration device, a pair of measurement terminals and a mode selector. The pair of RF-channels terminals is configured to send or receive measurement signals to or from an RF-channel of the tester. The calibration device is configured to perform a calibration of the RF-channel based on the measurement signals sent to, or received from, the RF-channel. The pair of measurement terminals is configured to send or receive measurement signals to or from the device under test. The mode selector is configured to connect, in a calibration phase, the pair or RF-channel terminals to the calibration device for calibrating the RF-channel and to connect, in a measurement phase, the pair of RF-channel terminals to the pair of measurement, terminals for routing measurement signals from the RF-channel to the device under test or vice versa.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 13/925,771 filed Jun. 24, 2013, which is a continuation ofInternational Application No. PCT/EP2010/070503, filed Dec. 22, 2010,both which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Embodiments of the present invention create a calibration module for atester, which can be used to calibrate an RF-part of the tester. Furtherembodiments of the present invention create a tester with anexchangeable calibration module.

RF sources and RF receivers in an automated test equipment (ATE) provideRF resources at connection pins to the device under test (DUT)interface. To achieve calibrated power level and enable scalar andvector (=s-parameter) measurements a per-pin-calibration isnecessitated. This is done either by an external calibration kit orcalibration robot which can connect to all RF pins arid routes the pinto measurement devices for transmit signals and provides a loop-back toa receiver input.

As a typical calibration kit has only one measurement capabilityconnectable to one input, all RF pins have to be calibrated one afterthe other. This leads to long calibration times and hence downtime ofthe ATE. One pin necessitates a calibration time in the range ofminutes. A potential ATE-System with several hundred pins wouldnecessitate many hours.

SUMMARY

According to an embodiment, an exchangeable calibration module for atester for testing a device under test may have: a pair of RF-channelterminals including a first RF-channel terminal and a second RF-channelterminal, wherein the pair of RF-channel terminals is configured to sendor receive measurement signals to or from an RF-channel of the tester; acalibration device configured to perform, a calibration of theRF-channel based on the measurement signals sent to, or received fromthe RF-channel; a pair of measurement terminals including a firstmeasurement and a second measurement terminal, wherein the pair ofmeasurement terminals is configured to send or receive measurementsignals to or from the device under test; a mode selector configured toconnect, in a calibration phase, the pair of RF-channel terminals to thecalibration device for calibrating the RF-channel and to connect, in ameasurement phase, the pair of RF-channel terminals to the pair ofmeasurement terminals for routing measurement signals from theRF-channel to the device under test, or for routing measurement signalsfrom the device under test to the RF-channel; and wherein the first RFchannel terminal is a cable connector and the second RF channel terminalis a cable connector.

According to another embodiment, a tester for communicating with adevice under test may have: an RF-channel; and an inventive exchangeablecalibration module, configured to send or receive measurement signals toor from the RF-channel, wherein the calibration module is configured toroute, in the measurement phase, measurement signals from the RF-channelto the device under test or to route, in the measurement phase,measurement signals from the device under test to the RF-channel.

Embodiments of the present invention create a calibration module for atester, testing a device under test. The calibration module comprises apair of RF-channel terminals comprising a first RF-channel terminal anda second RF-channel terminal, wherein the pair of RF-channel terminalsis configured to send or receive measurement signals to or from anRF-channel of the tester. The RF-channel may comprise an RF transmitport for transmitting measurement signals to the pair of RF-channelterminals and may comprise an RF receive port for receiving measurementsignals sent from the pair of RF-channel terminals.

The calibration module farther comprises a calibration device,configured to perform, (or support) a calibration of the RF-channelbased on the measurement signals sent to, or received from theRF-channel.

The calibration module further comprises a pair of measurement terminalscomprising a first measurement terminal and a second measurementterminal, wherein the pair of measurement terminals is configured tosend or receive measurement signals to or from the device under test.

The calibration module further comprises a mode selector to connect, ina calibration phase the pair of RF-channels to the calibration devicefor calibrating the RF-channels and to connect, in a measurement phase,the pair of RF-channel terminals to the pair of measurement terminalsfor routing measurement signals from the RF-channel to the device undertest and/or for routing measurement signals from the device under testto the RF-channel.

It is the key idea of the embodiments of the present invention that afaster calibration of an RF part of a tester can be achieved if the RFpart of the tester is separated into parts, which can be calibratedseparately from each other. In embodiments of the present invention, aRF part of the tester is separated into the RF-channel and into thecalibration device. The RF-channel can be calibrated using thecalibration device, therefore no additional calibration kit orcalibration robot is necessitated for calibrating the RF-channel.Furthermore, the calibration of the calibration modules can becalibrated separately on the RF-channel of the tester (e.g. outside thetester) confirming all ports and paths received concerning all signalpaths between the pair of RF-channel terminals and the pair ofmeasurement terminals.

By providing the calibration device in the calibration module, theinterior part of the RF-channel can be calibrated, so the complete pathup to the device under test connector (the pair of measurementterminals) of a tester can be computed. The calibration module may be,for example, exchangeable from the tester and may be pre-calibrated andrecalibrated in a factory of the manufacturer of the calibration module.In contrast to this, the RF-channel of the tester can be calibrated atthe customer site using the calibration module. The calibration of theRF part of a very complex tester or a very complex automated testequipment can therefore be performed within a downtime of minutesinstead of hours.

It is an advantage of embodiments of the present invention that a fasterrecalibration of an RF part of a tester can be achieved.

In the measurement phase, the calibration module may only be used forrouting the measurement signals from the RF-channels to the device undertest and the calibration device may be deactivated. Therefore, in themeasurement phase, the calibration module may only provide passivesignal paths from the RF-channel to the device under test, with noinfluence on the measurement signals routed from the RF-channel to thedevice under test and from the device under test to the RF-channel. Inthe measurement phase, the tester, to which the calibration module isconnected, is therefore, testing the device under test.

In the calibration phase, the calibration module may act as an activedevice providing calibration functions for the RF-channel.

According to some embodiments, the calibration device may perform thecalibration of the RF-channel by providing a loopback function, sensinga power of a measurement signal received at the RF-channel terminals orby providing a stimulus as a measurement signal at an RF-channelterminal. Therefore, the calibration device may perform a calibration byproviding a calibration environment for the RF-channel The calibrationmodule can furthermore transmit calibration results (e.g. a sensed powerof a measurement signal) to the RF-channel.

According to some embodiments, the calibration module may comprise acalibration memory holding calibration values for possible signal pathsbetween the pair of RF-channel terminals and the pair of measurementterminals. The calibration value may comprise transfer functions, forexample s-parameter for all ports (for all measurement terminals) of thecalibration module. These calibration values may be determined during amanufacturing process of the calibration module by the manufacturer ofthe calibration module and may be stored into the calibration memory.Furthermore, the calibration values may be recalibrated in certain timespans, for example, at the manufacturer. Therefore, no calibration ofthe calibration module at the customer site is necessitated. Thecalibration module may only comprise passive components between anRF-channel terminal and a measurement terminal, with a calibration of asignal path between the RF-channel terminals and the measurementterminals having a higher validity than a calibration of an RF-channel(comprising active components). With this, the calibration of thecalibration module, respectively of the signal paths of the calibrationmodule may be repeated in longer time intervals than the calibration ofthe RF-channel of the tester. Therefore, the calibration of theRF-channels may be performed more often than the calibration of thecalibration module. Therefore, it is advantageous that the calibrationof the RF-channels, which necessitates a shorter calibration interval,can happen at the customer site, wherein the calibration of thecalibration module, which has longer calibration intervals, can be doneat the manufacturer site.

According to further embodiments, the calibration module may comprise aplurality of measurement terminals. Therefore, a calibration of thecalibration module may be time consuming, as every measurement terminalof the calibration module may have to be calibrated. Embodiments solvethis problem by providing the exchangeable calibration module, thisenables a calibration of the calibration module outside the tester (e.g.at a manufacturer side). During the time of the calibration of thecalibration module, the tester may continue running using a replaced(freshly calibrated) calibration module. This concept reduces a downtimeof the automatic test equipment or of the tester on-site by using theprecalibrated calibration modules.

The calibration values stored in the calibration memory can be used bythe tester for calculating the channel properties (of the measurementterminals) in conjunction with the obtained calibration values for theRF-channel by using the calibration module.

In other words, embodiments of the present invention provide a conceptin which features of a calibration kit or calibration robot areintegrated into an (exchangeable) calibration module, which can beeasily accessed. This calibration module may contain calibratedstandards to perform a channel-based calibration and calibration data,e.g. s-parameters for all ports, which can be used for systemcalibration and provide calibration including the connection pins (themeasurement terminals) to a device under test interface (e.g. connectedto the device under test). This data (the calibration values) can bestored inside the exchangeable calibration module (e.g. in a calibrationmemory of the calibration module).

According to further embodiments, the calibration module may comprise aplurality of pairs of RF-channel terminals, wherein each pair ofRF-channel terminals is configured to communicate with a differentRF-channel of a tester. Furthermore, such a calibration module maycomprise a plurality of calibration devices and mode selectors, eachassociated to a pair of RF-channel terminals. Furthermore, such acalibration module may comprise a plurality of pairs of measurementterminals, each pair of measurement terminals being associated to a pairof RF-channel terminals.

In other words, the channel count of a calibration module according toan embodiment corresponds to the channel count of the frontend card (ofthe card in the tester holding the plurality of RF-channels). If thiscard contains four RxTx-channels (four RF-channels), the exchangeablemodules may contain eight input pins (8 RF-channel terminals or 4 pairsof RF-channel terminals).

Further embodiments of the present invention provide a tester or anautomatic test equipment, for communicating with a device under test (orfor testing the device under test). The tester comprises an RF-channel(or a plurality of RF-channels), and an exchangeable calibration moduleas it was described above, which is configured to send or receivemeasurement signals to or from the RF-channel. The calibration module isconfigured to route, in the measurement phase, measurement signals fromthe RF-channel to the device under test, or to route the measurementsignals from the device under test to the RF-channels.

Furthermore, the calibration module is configured to provide acalibration for the RF-channel of the tester. By having the exchangeablecalibration module, it can be achieved that the RF part of the tester,consisting of the RF-channel and the exchangeable calibration module,can be separated and can be separately calibrated, wherein the activecomponents (the RF-channels) can be calibrated more often at thecustomer site, and the passive components (the calibration module) canbe calibrated less often at the manufacturer site. This reduces thedowntime of the tester for calibration.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 shows a block schematic diagram of a calibration module embeddedin a tester, according to an embodiment;

FIGS. 2A-2B shows a block schematic diagram of a calibration moduleembedded in a tester, according to a further embodiment;

FIG. 3 shows a schematic top view on the calibration module from FIG. 2,and how it may be integrated into a tester; and

FIG. 4 shows a block schematic diagram of a tester according to anembodiment.

DETAILED DESCRIPTION OF THE INVENTION

Before embodiments of the present invention are described in detailusing the accompanying figures, it is to be pointed out that the sameelements or elements with the same function will be provided with thesame reference numerals and that a description of elements provided withthe same reference numerals is mutually exchangeable. Therefore, arepeated description of elements provided with the same referencenumerals is omitted.

FIG. 1 shows a block schematic diagram of a calibration module 100 for atester 102 for testing a device under test 104. In FIG. 1 thecalibration module 100 is shown as a component of the tester 102. Thecalibration module 100 may, for example, be an exchangeable component ofthe tester 102, which means that the calibration module 100 may bedetachable from the tester 102. Therefore, the calibration module 100may be an exchangeable card or part of the tester 102.

The calibration module 100 comprises a pair of 106 RF-channel terminalscomprising a first RF-channel terminal 106 a and a second RF-channelterminal 106 b. The pair 106 of RF-channel terminals is configured tosend or receive measurement signals 108 a, 108 b to or from anRF-channel 110 of the tester 102. For example, the first RF-channelterminal 106 a may be configured to receive a measurement signal 108 afrom the RF-channel 110 and the second RF-channel terminal 106 b may beconfigured to transmit a measurement signal 108 b to the RF-channel 110.

The calibration module 100 comprises a calibration device 112 which isconfigured to perform a calibration of the RF-channel 110 based on themeasurement signals 108 a, 108 b sent to, or received from, theRF-channel 110.

The calibration module 100 further comprises a pair 114 of measurementterminals comprising a first measurement terminal 114 a and a second,measurement terminal 114 b. The pair 114 of measurement terminals isconfigured to send or receive measurement signals 116 a, 116 b to orfrom the device under test 104. For example, the first measurementterminal 114 a may be configured to send a measurement signal 116 a tothe device under test 104 and the second measurement terminal 114 b maybe configured to receive a measurement signal 116 b from the deviceunder test 104.

The calibration module 100 further comprises a mode selector 118configured to connect, in a calibration phase, the pair 106 ofRF-channels to the calibration device 112 for calibrating the RF-channel110. The mode selector 118 is configured to connect, in a measurementphase, the pair 106 of RF-channel terminals to the pair 114 ofmeasurement terminals for routing measurement signals from theRF-channel 110 to the device under test 104, or for routing measurementsignals from the device under test 104 to the RF-channel 110. Forexample, the mode selector 118 may connect the first RF-channel terminal106 a to the first measurement terminal 114 a for routing themeasurement signal 108 a to the device under test 104, such that themeasurement signal 108 a corresponds to the measurement signal 116 a (orin other words, such that the measurement signal 108 a is themeasurement signal 116 a). Furthermore, the mode selector 118 mayconnect the second RF-channel terminal 106 b to the second measurementterminal 114 b for routing the measurement signal 116 b from the deviceunder test 104 to the RF-channel 110, such that the measurement signal116 b corresponds to the measurement signal 108 b (or in other words,such that the measurement signal 116 b is the measurement signal 108 b).

In other words, the mode selector 118 is configured to establish signalpaths between the pair 106 of RF-channel terminals and the pair 114 ofmeasurement terminals. The mode selector 118 as shown in FIG. 1 mayestablish a signal path between the first RF-channel terminal 106 a andthe first measurement terminal 114 a, and may establish another signalpath between the second RF-channel terminal 106 b and the secondmeasurement terminal 114 b.

The mode selector 118 may control a first switch 120 a for establishingthe signal path between the first RF-channel terminal 106 a and thefirst measurement terminal 114 a, and for connecting the firstRF-channel terminal 106 a to the calibration device 112. The modeselector 118 may further control a second switch 120 b for establishingthe signal path between the second RF-channel terminal 106 b and thesecond measurement terminal 114 b, and for connecting the secondRF-channel terminal 106 b to the calibration device 112.

The switches 120 a, 120 b may be implemented using switching transistorsor relays or PIN diodes.

The established signal path between the pair 106 of RF-channels and thepair 114 of measurement terminal may comprise passive components (suchas transistors, capacitors, inductors or signal paths of switches, suchas drain-source-paths or emitter-collector-paths).

This means the measurement signals routed from the RF-channel 110 to thedevice under test 104, or from the device under test 104 to theRF-channel 110 may be routed only along passive components. In contrastto this, the RF-channel 110 may comprise active components such asamplifiers or signal generators, which have to be calibrated more oftenthan the passive components of the calibration module 100. Therefore, acalibration of the RF-channel 110 may be necessitated more often than acalibration of the calibration module 100. Therefore, the calibrationmodule 100 enables a separate calibration of the RF-channel 110 and thecalibration module 100. Therefore, the RF-channel 110 may be calibratedusing the calibration module 100 at the customer site, which means thatthe calibration module 100 remains in the tester 102 during calibrationof the RF-channel 110. For calibrating the calibration module 100, thecalibration module 100 can be removed from the tester 102 and can bereplaced with another (freshly calibrated) calibration module, forexample, having the same functions as the calibration module 100. Theremoved calibration module 100 may be sent to the manufacturer of thecalibration module 100 for calibrating itself for calibrating thecalibration module 100 at the manufacturer site.

As can be seen from FIG. 1, the mode selector 118 may be configured todisconnect the pair 106 of RF-channel terminals from the calibrationdevice 112 in the measurement phase, such that the calibration device112 does not influence a measurement perforated on the device under test104. In the example shown in FIG. 1, the calibration module 100 is inthe measurement phase, meaning that the switches 120 a, 120 b connectthe pair 106 of RF-channels to the pair 114 of measurement terminals andthe calibration device 112 is disconnected from the pair 106 ofRF-channels.

Furthermore, the mode selector 118 may be configured to disconnect thepair 114 of measurement terminals (by switching the switches 120 a, 120b) from the pair 106 of RF-channel terminals in the calibration phase,such that the calibration of the RF-channel 110 is not influenced by thepair 114 of measurement channels and the connected device under test104.

FIG. 2 shows a block schematic diagram of a calibration module 200 for atester 202 for testing a device under test 104. In the example shown inFIG. 1, the calibration module 200 is embedded in the tester 202 and isconnected to an RF-channel 210 of the tester 202. The calibration module200 may, in its functionality, be equal to the calibration module 100and may comprise the additional features shown in FIG. 2. Furthermore,the RF-channel 210 may, it its functionality, be equal to the RF-channel110 of the tester 102.

The calibration module 200 differs from the calibration module 100 inthat it comprises a plurality of measurement terminals 114 a-1 to 114a-4, 114 b-1 to 114 b-4, The plurality of measurement terminals 114 a-1to 114 a-4, 114 b-1 to 114 b-4 can be separated in a first group ofmeasurement terminals 114 a-1 to 114 a-4 and a second group ofmeasurement terminals 114 b-1 to 114 b-4. The second group ofmeasurement terminals 114 b-1 to 114 b-4 and the first group ofmeasurement terminals 114 a-1 to 114 a-4 are disjunct. The calibrationdevice 200 further comprises a mode selector 218, a functionality ofwhich is similar to a functionality of the mode selector 118 from thecalibration module 100. The functionality of the mode selector 218 isdifferent from the functionality of the mode selector 118 in that it mayhandle a higher number of measurement terminals of the calibrationmodule 200, compared to the calibration module 100. Therefore, the modeselector 218 provides a higher flexibility in routing measurementsignals from the RF-channel 210 to the device under test 104, or fromthe device under test 104 to the RF-channel 110. The mode selector 218differs from the mode selector 118 in that it comprises, additionally tothe switches 120 a, 120 b, a cross switch 222 and a multiplexer 224. Themode selector 218 may be configured to provide different signal pathsbetween the pair 106 of RF-channels and the plurality of measurementterminals 114 a-1 to 114 a-4, 114 a-1 to 114 b-4. By using the crossswitch 222 and the multiplexer 224, the mode selector 218 may beconfigured to connect in the measurement phase, the pair 106 ofRF-channel terminals, to a chosen pair of measurement terminals out ofthe plurality of measurement terminals 114 a-1 to 114 a-4, 114 b-1 to114 b-4, such that a first measurement terminal of the pair ofmeasurement terminals which is connected to the pair 106 of RF-channelterminals is part of the first group of measurement terminals 114 a-1 to114 a-4 and a second measurement terminal of the pair of measurementterminals which is connected to the pair 106 of RF-channel terminals ispart of the second group of measurement terminals 114 b-1 to 114 b-4.The mode selector 218 may, for example, connect the first RF-channelterminal 106 a to one of the measurement terminals 114 a-1 to 114 a-4out of the first group of measurement terminals and may connect thesecond RF-channel terminal 106 b to one of the measurement terminals 114b-1 to 114 b-4 out of the second group of measurement terminals. Thismechanism may be advantageous, for example, in the ease in which thefirst group of measurement terminals 114 a-1 to 114 a-4 are dedicatedtransmit terminals and the second group of measurement terminals 114 b-1to 114 b-4 are dedicated receive terminals, or vice-a-versa.

The measurement terminals 114 a-1 to 114 a-4, 114 b-1 to 114 b-4 can beconnected to a device under test board 204 (DUT-board 204) onto whichthe device under test 104 is mounted. The DUT-board 204 is thereforeused to connect the device under test 104 to the tester 202 using themeasurement terminals 114 a-1 to 114 a-4, 114 b-1, to 114 b-4. Thedevice under test board 204 may be a customer- and device-specific boardwhich can be developed by the customer who wants to test its devices.

In the example in FIG. 2 the first RF-channel terminal 106 is connectedto a transmit port 232 of the RF-channel 210 and the second RF-channelterminal 106 b is connected to a receive port 234 of the RF-channel 210.

According to further embodiments, the calibration module 200 maycomprise a calibration memory 226 holding calibration values forpossible signal paths between the pair 106 of RF-channel terminals andthe measurement terminals 114 a-1 to 114 a-4, 114 b-1 to 114 b-4. Inother words, the calibration memory 226 may comprise calibration valuesor calibration data for each measurement terminal of the measurementterminals 114 a-1 to 114 a-4, 114 b-1 to 114 b-4 of the calibrationmodule 200. For example, the calibration memory 226 may comprises-parameters for the signal paths between the pair 106 of RF-channelterminals and the measurement terminals 114 a-1 to 114 a-4, 114 b-1 to114 b-4. Based on these s-parameters, characteristics (e.g. an insertionloss) of the calibration module 200 may be calculated. These calculatedcharacteristics can be used for calculating the whole RF-part (includingthe RF-channel 210 and the calibration module 200) of the tester 202.

Its calibration values may be programmed into the calibration memory 226by the manufacturer of the calibration module 200, for example, after aproduction of the calibration module 200. The customer using thecalibration module 200 for calibrating the RF-channel 210 of the tester202 does not need to perform a calibration of the calibration module200, as this has already been done by the manufacturer of thecalibration module 200. The tester 202 may use the calibration valuesfor the different signal paths between the pair 106 of RF-channels andthe different measurement terminals 114 a-1 to 114 a-4, 114 b-1 to 114b-4 in conjunction with the calibration values obtained by calibratingthe RF-channel 210, using the calibration module 200, for calculatingthe whole RF paths from the RF-channel 210 to the device under testboard connector (to the measurement terminals 114 a-1 to 114 a-4, 114b-1 to 114 b-4) or for calculating a transfer characteristic of thewhole RF-part of the tester 202. If a recalibration of the calibrationmodule 200 is needed, the calibration module 200 may be removed from thetester 202 and may be sent to the manufacturer 202 for performing arecalibration of the calibration module 200. The calibrated values ofthe calibration module 200 may be stored in the calibration memory 226.Therefore, there is no longer the need for a calibration kit or acalibration robot at the customer site. A removed calibration module 200can be easily replaced by (a freshly calibrated) calibration module ofthe same type, thus reducing a downtime of the tester 202.

In dependence on an established signal path between the pair 106 ofRF-channel terminals and the measurement terminals 114 a-1 to 114 a-4,114 b-1 to 114 b-4 the calibration module 200 may provide acorresponding calibration value to the tester 200 for each establishedsignal path in the measurement phase, such that the tester 200 cancalculate the transfer function of the complete signal path from thegeneration of the measurement signals in the RF-channel 210 to thedevice under test 104 and vice-a-versa.

The calibration memory 226 may further comprise calibration values forthe calibration device 212 of the calibration module 200. Thecalibration module 200 may be configured to provide the calibrationvalues for the calibration device 212 to the RF-channel 210, or in otherwords, to the tester 202. These calibration values for the calibrationdevice 212 may be used for correcting failures occurring in thecalibration generated internally in the calibration device 212. Thecalibration module 200 may therefore be configured to provide acorrection value for the calibration device 212 which can be used tominimize failures introduced by the calibration device 212.

Furthermore, the calibration memory 226 may hold a (unique) serialnumber associated to the calibration module 200. The serial number maybe transmitted to the tester 202 for identifying the calibration 200 andfor distinguishing between different calibration modules. This enablesthat in the case of a replacement of the calibration module thecalibration values of the new calibration module are transmitted to thetester 202 for recalculating the RF-part of the tester 202 using thecalibration values of the new calibration module instead of thecalibration values of the calibration module which was replaced by thenew calibration module.

The calibration module 200 may further comprise an information terminal228 by which the calibration module 200 may transmit the calibrationvalues to the RF-channel 210 or the tester 202. The information terminal228 may further be used to receive a mode selection signal from thetester 202, based on which the mode selector 218 switches from thecalibration phase to the measurement phase and from the measurementphase to the calibration phase.

As previously described, the mode selector 218 may be configured toestablish different signal paths between the different measurementterminals 114 a-1 to 114 a-4, 114 b-1 to 114 b-4 of the calibrationmodule 200 and the pair 106 of RF-channel terminals in the measurementphase. The mode selector 218 may be configured to extract an informationout of the mode selection signal received from the RF-channel 210. Theextracted information may define which signal paths have to beestablished between the pair 106 of RF-channels and the measurementterminals 114 a-1 to 114 a-4, 114 b-1 to 114 b-4, and which not, suchthat the mode selector 218 may, in response to the information extractedfrom the mode selection signal, establish the signal paths. Furthermore,the mode selector 218 may based on the extracted information out of themode selection signal connect a certain first measurement terminal outof the plurality of measurement terminals 114 a-1 to 114 a-4, 114 b-1 to114 b-4 to the first RF-channel terminal 106 a, and may connect acertain second measurement terminal out of the plurality of measurementterminals 114 a-1, to 114 a-4, 114 b-1 to 114 b-4 to the secondRF-channel terminal 106 b.

In other words, the mode selector 118 may connect the pair 106 ofRF-channel terminals to a pair of measurement terminals out of theplurality of measurement terminals 114 a-1 to 114 a-4, 114 b-1 to 114b-4 based on the information extracted from the mode selection signal.

The mode selector 218 is configured to establish the signal, pathsbetween the pair 106 of RF-channels and the measurement terminals 114a-1 to 114 a-4, 114 b-1 to 114 b-4 by switching the switches 120 a, 120b and by switching the cross switch 222 and the multiplexer 224. Theselector 218 may therefore comprise a switch controller 230 configuredto receive the mode selection signal and to extract the informationdefining which signal paths have to be established in the measurementphase and to establish the signal paths defined in the extractedinformation by switching the switches 120 a, 120 b, the cross switch 222and the multiplexer 224.

The cross switch 222 is configured to connect in a first stage of themeasurement phase, the first RF-channel terminal 106 a to a firstmeasurement terminal (e.g. to the measurement terminal 114 a-1) and thesecond RF-channel terminal 106 b to a second measurement terminal (e.g.to the measurement terminal 114 b-1). In a second stage of themeasurement phase the cross switch 222 may connect the first RF-channelterminal 106 a to the second measurement terminal 114 b-1 and the secondRF-channel terminal 106 b to the first measurement terminal 114 a-1. Inother words, the cross switch 222 is configured to swap, transmit andreceive ports (TxRx paths).

Furthermore, the cross switch 222 may be configured to connect the pair106 of RF-channel terminals to the pair of measurement terminals 114a-1, 114 b-1, such that during the first stage and the second stage ofthe measurement phase, each measurement terminal 114 a-1, 114 b-1 isconnected to at maximum of one RF-channel terminal 106 a, 106 b.

Or in other words, the cross switch 222 may be used to swap the firstgroup of measurement terminals 114 a-1 to 114 a-4 with the second groupof measurement terminals 114 b-1 to 114 b-4 such that in the first stageof the measurement phase, a measurement terminal of the first group ofmeasurement terminals 114 a-1 to 114 a-4 is connected to the firstRF-channel terminal 106 a and a measurement terminal out of the secondgroup of measurement terminals 114 b-1 to 114-4 is connected to thesecond RF-channel terminal 106 b and vice-a-versa in the second stage.

The multiplexer 224 is configured to connect a measurement terminal outof the first group of measurement terminals 114 a-1 to 114 a-4 and ameasurement terminal out of the second group of measurement terminals114 b-1 to 114 b-4 to the cross switch 222. The multiplexer 224 shown inFIG. 1 has a fan-out of 2:8, which means it has two input ports andeight output ports. According to further embodiments, anothermultiplexer comprising different fan-outs may also be used instead ofthe multiplexer 224.

In other words, the multiplexer 224 is configured to connect the pair106 of RF-channel terminals to a pair of measurement terminals, suchthat a first measurement terminal of the first pair of measurementterminals (e.g. the measurement terminals 114 a-1) is comprised in thefirst group of measurement terminals 114 a-1 to 114 a-4 and the secondmeasurement terminals of the pair of measurement terminals (e.g. themeasurement terminal 114 b-1) is comprised in the second group ofmeasurement terminals 114 b-1 to 114 b-4.

The calibration device 212 provides a loop back functionality forshortening the first RF-channel 106 a and the second RF-channel 106 bduring the calibration phase. Furthermore, the calibration device 212comprises a power meter 236, for example, to sense the power of themeasurement signal 108 a transmitted from the RF-channel 210.

Furthermore, the calibration device 212 provides a stimulus generator238, for example, to generate the measurement signal 108 b as areference stimulus for the RF-channel 210.

According to another embodiment, the calibration device 212 may compriseonly one, or an arbitrary combination, of the features shown in FIG. 2.

Therefore, the calibration device 212 provides different calibrationfunctions for calibrating an interior part of the RF-channel 210, suchthat an external calibration kit or calibration robot for calibratingthe interior part of the RF-channel 210 is no longer needed as thenecessitated functions for calibrating the RF-channel 210 are integratedin the calibration module 200.

The functionality of the calibration module 200 is summarized asfollows.

The concept of the present invention provides an integration of thecalibration module into the TxRx channel (or into the RF part) of atester. This system (the RF part) is separated into parts, theRF-channel 210 inside the ATE or inside the tester 202 and a separatepart (the exchangeable calibration module 200) next to the device undertest interface. This separate part (which is advantageously anexchangeable module) can be calibrated outside the ATE concerning allports (alt measurement terminals) and paths (all signal paths). Thiscalibration module 200 provides calibration devices (the power meter236, the stimulus generator 238, and the loop back functionality or acombination of such devices) to also calibrate the interior part of theRF-channel, so that the complete path up to the device under testconnector (to the measurement terminals 114 a-1 to 114 a-4, 114 b-1 to114 b-4) can be computed. This calibration can be made simultaneously inall TxRx channels (in all RF parts of the tester 200). The principle panof the calibration (the calibration of the calibration module 200) canbe done in the factory, calibration data can be linked to the embeddedRF calibration device (to the calibration module 200, for example,stored in the calibration memory 226), which can be easily exchanged atthe customer site and sent back to the manufacturer for recalibration.The calibration of the RF part of a very complex ATE can be performedwithin a downtime of minutes instead of hours.

Embodiments integrate the features of a calibration kit or a calibrationrobot are integrated into an exchangeable device (into the calibrationmodule 200), which can be easily accessed. This calibration modulecontains calibrated standards to perform a channel-based calibration andcalibration data, e.g. s-parameters for all ports (for all measurementterminals 114 a-1 to 114 a-4, 114 b-1 to 114 b-4), which can be used forsystem calibration and to provide calibration, including the connectionpins, to the device under test interface. This data (the calibrationdata or the calibration values) can be stored inside the exchangeablecalibration module 200 (e.g. inside the calibration memory 226).

The channel count of the calibration module 200 corresponds to thechannel count of the front-end card of the tester. If this card containsfour TxRx channels, the calibration modules may contain eight input pins(e.g. four pairs of RF-channel terminals), a loop back feature, a crossswitch, a power detector and a switching matrix (the multiplexer)providing a fan-out of 8, 16, 32, or even more pins. According tofurther embodiments, the calibration module may comprise a calibrationdevice 212, a cross switch 222 and a multiplexer 224 for each pair 106of RF-channel terminals that it comprises. Therefore, a parallelcalibration of each RF-channel connected to the calibration module 200can be enabled.

A customer may choose between a high performance module with fewinternal switches (e.g. a low fan-out multiplexer) or a low-cost systemwith many pins or many measurement terminals (e.g. a high fan-outmultiplexer) and a significant reduction of the cost per pin.

FIG. 2 shows a part of a system level block diagram incorporating theconcept of the present invention. The exchangeable calibration moduleprovides loop-back functionality for calibration, the cross switch 222to swap the TxRx path and the multiplexer 224 with the desired fan-out.According to a further embodiment, the cross switch 222 may also beintegrated as part of the RF-channel 210 for swapping the transmit port232 with the receive port 234.

The calibration module 200 may be connected to the RF-channel 210 usingcables, for example, coaxial cables. The first RF-channel terminal 106 aand the second RF terminal 106 b may comprise cable connectors or may becable connectors themselves. Furthermore, the information terminal 228may comprise a cable connector or may be a cable connector itself. Themeasurement terminal 114 a-1 to 114 a-4, 114 b-1 to 114 b-4 may comprisemeasurement pins or measurement pads for connecting to the device undertest 104 or to the device under test board 204. For example, themeasurement terminals 114 a-1 to 114 a-4, 114 b-1 to 114 b-4 maycomprise pogo pins for connecting the device under test board 204. Thedevice under test board 204 may comprise corresponding pogo pins forconnecting to the measurement terminals 114 a-1, to 114 a-4, 114 b-1 to114 b-4. Therefore, the calibration module 200 may be easily exchangedfrom the tester 203 by disconnecting the cables between the RF-channel210 and the calibration module 200.

FIG. 3 shows a schematic top view of a calibration module 300 accordingto an embodiment, which is fastened in a tester. In other words, FIG. 3shows a schematic drawing of a calibration module 300. This calibrationmodule 300 is accessible from the top (of the tester) and can easily beunfastened without the need for opening the tester or ATE.

As can be seen in FIG. 3, the calibration module 300 comprises cableconnectors 106 a, 106 b, 228 (which correspond to the RF-channelterminals 106 a, 106 b and the information terminal 228).

In addition, the calibration module 300 comprises n measurementterminals 114 a-1 to 114 a-n, being associated to a first group ofmeasurement terminals. Furthermore, the calibration module 300 comprisesn measurement terminals 114 b-1 to 114 b-n being associated to a secondgroup of measurement terminals. The measurement terminals 114 a-1 to 114a-n, 114 b-1 to 114 b-n may, for example, be pogo pins for connecting tothe device under test interface board 204.

According to further embodiments, the association to different groups ofthe measurement terminals is optional meaning that the differentmeasurement terminals of the calibration module 300 may not necessarilybe divided into disjunct groups.

Furthermore, the calibration module 300 comprises fasteners 302 a, 302 bfor fastening the calibration module 300 in the tester. The tester maycomprise a fastener 304 which is adapted to the fasteners 302 a, 302 bof the calibration module 300.

The mechanical solution shown in FIG. 3 consists of an easilyexchangeable unit (the calibration module 300) providing the pins fordocking to the DUT load board 204, including means for repeatable,reliable connections with mechanical tolerances. This module shown inFIG. 3 accommodates resources for one or more channels.

FIG. 4 shows a schematic block diagram of a tester 402 according to anembodiment, connected to a device under test board 404 holding a deviceunder test 104. According to further embodiments, the device under testboards 404 may also hold a plurality of devices under test 104 which areto be tested by the tester 402.

The tester 402 comprises a calibration module 400, a functionality ofwhich is similar to the functionality of the calibration module 200shown in FIG. 2. The calibration module 400 differs in that it comprisesa plurality of calibration sub-modules 400 a to 400 m, wherein eachcalibration sub-module 400 a to 400 m is connected to an RF-channel210-1 to 210-m of the tester 402. Each calibration sub-module 400 a to400 m may be similar to the calibration module 200 such that acalibration of the RF-channels 210-1 to 210-m can be simultaneouslyperformed for all RF-channels 210-1 to 210-m. Each calibrationsub-module 400 a to 400 m may comprise a mode selector and a calibrationdevice which are independent from the mode selector and calibrationdevices of the other calibration sub-modules. Each of the calibrationsub-modules 400 a to 400 m can be connected to its associated RF-channel210-1 to 210-m using cables, for example, each calibration sub-module400 a to 400 m may be connected to its associated RF-channel 210-1 to210 m using three cables (one cable per RF-channel terminal and onecable for the information terminal) for exchanging measurements signals,calibration values and the mode selection signal between the calibrationsub-module and its associated RF-channel.

According to a further embodiment, the calibration module 400 may alsocomprise a combined information terminal or information connector fortransmitting calibration values and switch mode selection signals forall of the calibration sub-modules 400 a to 400 m, for example, using a(serial) bus system.

The tester 402 further comprises a central processing module 403 whichis configured to control the RF-channels 210-1 to 210-m. The centralprocessing module 403 may be configured to calculate RF signal paths foreach RF-channel 210-1 to 210-m and its associated calibrated sub-modules400 a to 400 m, based on the calibration of the RF-channel 210-1 to210-m, which can be performed using the associated calibratedsub-modules 400 a to 400 m and the calibration values for the associatedcalibration sub-modules 400 a to 400 m, which are stored in calibrationmemories of the calibration sub-module 400 a to 400 m on the calibrationmodule 400.

Each calibration sub-module 400 a to 400 m can be connected to thedevice under test 204 using a plurality (n₁ to n_(m)) of measurementterminals, measurement pads, or measurement pins, for example,measurement pogo pins.

The tester 402 may comprise, as mentioned before, a system (e.g. afastener) for holding the calibration module 400 inside the tester 402.The tester 402 may further comprise a holding means for holding thedevice under test interface board 404.

In the following, aspects and advantages of the embodiments of thepresent invention will be summarized.

An advantage of embodiments is that embodiments reduce an ATE downtimeon site by using pre-calibrated modules (by using the calibrationmodules 100, 200, 400) as a calibration for an active channel (for theRF-channels 110, 210, 210-a to 210-m) and a passive output path (thesignal pass established in the calibration modules) can be doneseparately. The channel property per pin (per measurement terminal), arecalculated with this data (e.g. using the central processing module403). It has been found that the validity time of the passive components(used in the signal path of the calibration modules) is significantlylonger than of the active components (e.g. of the RF-channels).Therefore, it is an advantage of the present invention that only passivecomponents are used in the pre-calibrated module (at least in the signalpaths of the pre-calibrated calibration modules). Therefore, the partsof an RF-part of a test which have to be calibrated more often can becalibrated at the customer site using calibration modules according toembodiments. The calibration modules, which have to be calibrated lessoften can be pre-calibrated and recalibrated at the manufacturer site ofthe calibration module. Therefore, calibration robots or calibrationkits are no longer necessitated at the customer site.

Another advantage is the use of the precalibrated exchangeable modules,as all ports of the exchangeable module (of the calibration modules) arecharacterized in the factory, and calibration data can be stored in theinternal memory (in the calibration memory 226). As mentioned before,the modules (the calibration modules) can be recalibrated outside theATE after the calibration data of these modules have expired.

Another advantage is that the calibration modules are easilyexchangeable, as the modules can be mounted directly at the DUTinterface, the modules can be accessed without power down of the ATE. Ahot plug feature of the ATE can detect an exchange and trigger furthersteps. In other words, a tester, according to an embodiment may beconfigured to detect an exchange of a calibration module and may triggerfurther steps up on a detection of a new (replaced) calibration module.

Another advantage is the fast system level calibration as a calibrationmodule can comprise calibration devices per RF-channel (such as shown inFIG. 4 with the calibration sub-module 406 a to 460 m). Therefore, onlya little, possibly massive parallel, calibration needs to be done in theATE, including the cables from the TxRx channel (RF-channel) to theexchangeable module.

Another advantage is the loopback capability of the exchangeable module,as no external equipment is necessitated for the calibration of the Txand Rx cables as a loopback connection can be provided internally by theexchangeable module (by a calibration device of the exchangeablemodule).

A further advantage is the easy installation in the ATE, as the overallnumber of cables is significantly decreased by using a switching matrix(e.g. the multiplexer 224) close to the DUT board instead of inside thechannel module (inside an RF-channel), which reduces the number ofsensitive RF cables inside the ATE, so that thicker cables with betterRF properties can be used and cabling still necessitates less space.

An even further advantage is the flexible fan-out and the cross switch224 as the switching module (the mode selector 218) can contain a crossswitch 222 and different fan-outs, for example, 1:1, 1:2, 1:3, 1:4 oreven more (depending on the used multiplexer). The customer can easilychange from a high-performance direct out to a “low cost per pin”fan-out (depending on the used multiplexer).

Another advantage is the direct access to the TxRx card (to theRF-channel of the tester) as the TxRx port (e.g. the transmit port 232and the receive port 234) is/are accessible after the removal of theswitching module (of the calibration module). Therefore, a direct accessis possible for debugging.

Another advantage is the direct docking of the DUT at the RF ports whichare directly docked to the customers DUT board (e.g. using pogo pins).No further embedding of cables between the calibration plane (thecalibration module) and the load board is necessitated.

Another advantage is can be achieved by using a status indicator forindicating the calibration status of the module to a user to easeidentification of modules necessitating exchange. In other words, acalibration module according to an embodiment may comprise a calibrationindicator indicating its status of calibration. This indicator may, forexample, show how many days are left until the next calibration of thecalibration module is necessitated.

To summarize, in the embodiments the TxRx channel is separated into twoparts, the first being the RF-channel inside the ATE, the second (thecalibration module) as part of the device under test (DUT) interface.Both parts are connected to each other by cables.

The part of the DUT interface (the calibration module) is calibratedconcerning its transfer functions and contains calibration devices tocalibrate the interior part (the RF-channel). The transfer function ofthe complete path (of the complete RF part) can be computed andcalibration is valid op to the DUT interface.

Calibration modules according to embodiments can be easily exchanged.

Embodiments provide a concept of embedding of an RF calibration into atransmit-receive (TxRx) channel and enabling significant calibrationtime reduction.

Some embodiments provide a calibration module wherein measurementterminals comprise measurement pins or measurement pads for connectingthe measurement terminals to a device under test.

Further embodiments provide a calibration module wherein measurementterminals comprise pogo pins for connecting the measurement terminals toa device under test interface board holding a device under test.

Further embodiments provide a calibration module comprising a fasteningsystem for fastening the calibration module in a tester.

Some embodiments provide a tester comprising a fastener for holding andfastening a calibration module inside the tester.

Further embodiments provide a tester, wherein a calibration modulecomprises measurement pins or measurement pads for connecting a deviceunder test interface board to the tester, the device under testinterface board holding a device under test and wherein the testerfurther comprises a holder for holding the device under test interfaceboard.

Although each dependent claim is dependent on only one foregoing claim,other combinations of the claims do also form possible embodiments,except for cases in which claims are contradictory.

While this invention has been described in terms of several advantageousembodiments, there are alterations, permutations, and equivalents whichfall, within the scope of this invention. It should also be noted thatthere are many alternative ways of implementing the methods andcompositions of the present invention. It is therefore intended that thefollowing appended claims be interpreted as including all suchalterations, permutations, and equivalents as fall within the truespirit and scope of the present invention.

1. A method comprising: coupling radio frequency channel (RF-channel)terminals, during a calibration phase, to a calibration device, whereinthe RF-channel terminals are configured to send or receive measurementsignals to or from an RF-channel of an automatic test equipment (ATE);calibrating, by the calibration device during the calibration phase, theRF-channels based on measurement signals routed between the RF-channelterminals and the calibration device; coupling the radio RF-channelterminals, during a measurement phase, to measurement terminals, whereinthe measurement terminals are configured to send or receive measurementsignals to or from a device under test (DUT); and measuring, during themeasurement phase, the measurement signals routed between the RF-channelterminals and the measurement terminals.
 2. The method according toclaim 1, wherein calibrating the RF-channels comprises storing acalibration value determined from calibrating the RF-channels.
 3. Themethod according to claim 2, wherein calibrating the RF-channels furthercomprises calculating an RF path from the RF-channel to the DUT basedupon the determined calibration value.
 4. The method according to claim1, wherein the calibration device does not influence the measurements ofthe measurement signals routed between the RF-channel terminals and themeasurement terminals during the measurement phase.
 5. The methodaccording to claim 1, wherein the measurement terminals do not influencethe calibration of the RF-channels by the calibration device during thecalibration phase.
 6. The method according to claim 1, wherein the DUTdoes not influence the calibration of the RF-channels by the calibrationdevice during the calibration phase.
 7. The method according to claim 1,wherein the calibration device is configured to loopback a measurementsignal on a first RF-channel terminal to a second RF-channel terminal.8. A method comprising: establishing, during a calibration phase,calibration signal paths between a radio frequency (RF) resource of anautomatic test equipment (ATE) and a calibration device of the ATE;calibrating, by the calibration device during the calibration phase, theRF resource of the ATE based on measurement signals routed between theRF resource and the calibration device across the calibration signalpaths; and establishing, during a measurement phase, measurement signalpaths between the RF resource and a device under test (DUT) for routingthe measurement signals.
 9. The method according to claim 8, wherein thecalibration signal paths comprise passive components only.
 10. Themethod according to claim 8, wherein the RF resource includes one ormore active components.
 11. The method according to claim 8, furthercomprising storing calibration values determined from calibrating the RFresource for the calibration signal paths.
 12. The method according toclaim 8, wherein the calibration signal paths do not influence themeasurement signal paths during the measurement phase.
 13. The methodaccording to claim 8, wherein the measurement signal paths do notinfluence the calibration signal paths during the calibration phase. 14.The method according to claim 8, wherein establishing measurement signalpaths further comprises establishing different signal paths betweendifferent RF resources.
 15. A calibration module comprising: a means forrouting, in a calibration phase, measurement signals between a radiofrequency (RF) resource of a tester and a means for calibrating; themeans for calibrating, in the calibration phase, the RF resource basedon the measurement signals; and a means for routing, in a measurementphase, the measurement signals between the RF resource and a deviceunder test (DUT).
 16. The calibration module of claim 15, wherein themeans for routing, in a calibration phase, measurement signals includesa cross bar switch between the RF resource and the means forcalibrating.
 17. The calibration module of claim 15, wherein the meansfor calibrating comprises a power meter.
 18. The calibration module ofclaim 15, wherein the means for calibrating comprises a stimulusgenerator.
 19. The calibration module of claim 15, wherein the means forcalibrating comprises a loop back function.
 20. The calibration moduleof claim 15, wherein the means for calibration comprises an exchangeablemeans for calibration.